Apparatus for folding blades without changing pitch due to folding

ABSTRACT

A helicopter rotor has a blade mounted for folding movement. The blade is also mounted for feathering movement about its longitudinal axis and has a blade horn connected to a swashplate by linkage mechanism which provides a zero alpha pitch coupling during blade folding.

United States Patent Ferris 1 1 Apr. 1, 1975 [54] APPARATUS FOR FOLDINGBLADES 2,653,576 11/1953 Mosinskis 416/143 WITHOUT CHANGING PITCH DUE TO3,428,132 2/1969 Vacca 416/143 3,484,175 12/1969 Vacca 416/143 FOLDING[75] Inventor: Donald L. Ferris, Newton, Conn.

[73] Assignee: United Aircraft Corporation, East Hartford. Conn.

[22] Filed: Nov. 1, 1973 [2]] App]. No.1 411,863

152] US. Cl. 416/143 [51] Int. CL... 1164c 11/06, B64c 11/28, B64c 27/50[58] Field of Search 416/142, 143; 244/6, 7 A

156] References Cited UNITED STATES PATENTS 2.430.767 11/1947 Hirsch416/147 Primary E.\'amtnerEverette A. Powell, Jr. AssistantExaminer-Louis J. Casaregola Attorney, Agent, or Firm-Maurice B. Tasker[57] ABSTRACT A helicopter rotor has a blade mounted for foldingmovement. The blade is also mounted for feathering movement about itslongitudinal axis and has a blade horn connected to a swashplate bylinkage mechanism which provides a zero alpha pitch coupling duringblade folding.

8 Claims, 8 Drawing Figures PATENTED 3.874. 817

SHCEI10F3 TJATENIEBAPR 1191a SHEET 3 OF 3 FIG-5 FIG-3 FIC3-8 APPARATUSFOR FOLDING BLADES WITHOUT CHANGING PITCH DUE TO FOLDING BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates tohelicopter rotors and particularly to rotors which are used inconnection with convertiplanes in which the helicopter rotor blades arefolded in flight. More particularly the present invention relates to anovel linkage mechanism between the suashplate and the horns of therotor blades which permits folding of the blades without disconnectionof the linkage or other operating mechanism. Further the presentinvention permits blade folding without change of blade pitch. i.e. zeroalpha pitch coupling or. if pitch coupling is desired. without change ofthe predetermined pitch coupling.

2. Description of the Prior Art US. Pat. No. 3.484.l75. issued Dec. I6,I96) to L.

Vacca et al. shows blade folding about a vertical hinge in in a rigidmotor. By putting the mechanism of this invention in place of rod I80ofthis patent. blade fold ing in a rigid rotor could be provided withzero pitch coupling.

US. Pat. No. 3.515.500 issued June 2. I970 to J. H.

Nachod. shows a blade folding rotor in which the blades are foldableabout the blade flapping axis after the pitch changing servos have beendisconnected to make the normal pitch changing mechanism ineffective. Bysubstituting the mechanism of the present invention in rod I40 of eachblade the disconnection of the servos could be avoided.

US. Pat. No. 3.42%.l32. issued to Luigi Vacca et al on Feb. l8. I969.shows a typical example ofa helicopter having an articulated rotorincluding a lag-lead hinge inherently providing a degree of alphacoupling during flight operations. Applicant's novel mechanism can beinserted in link 80 of Vacca between the swashplate and the blade hornand the blade can then lead or lag in normal flight with zero alphacoupling. In modified form. adjustable alpha coupling can be provided.

The patent to H. Hirsch U.S. Pat. No. 2.430.767. issued Nov. ll. I947.shows a fully articulated blade structure in which the motiontransmitting linkage for changing blade pitch includes a universal jointlocated at the lag-lead hinge about which blade fold can presumablyoccur. Also the patent to Mosinskis. U.S. Pat. No. 2.658.576. issuedNov. 10, I953. shows another helicopter pitch control system whereinlinks 36 and 48 in the pitch control linkage are aligned generally alongthe blade fold axis and by means of bearing assembly 46 permit bladefolding without change of blade pitch. The present invention provides anew and improved structure for permitting blade folding without changeof blade pitch which is particularly advantageous in convertiplaneswherein blade folding takes place in flight.

SUMMARY OF THE INVENTION The present invention is directed to ahelicopter rotor having an improved. extremely simple and reliablemechanism in the linkage connecting the rotatable swashplate member andeach blade horn by which the blades can be folded either manually orautomatically without the need for disconnecting anything connected withthe blades or their operating mechanism and wherein the blades arefolded without change of pitch. i.e. zero alpha pitch coupling BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the helicopterrotor embodying the improved linkage mechanism ofthc present invention'.

FIG. 2 is a sectional elevation on an enlarged scale of part of therotor of FIG. 1;

FIG. 3 is a simplified. somewhat diagrammatic plan view of the linkagemechanism in the flight position of the blade. the blade horn beingomitted in this view;

FIG. 4 is an elevation of FIG. 3;

FIG. 5 is a plan view similar to FIG. 3 showing the linkage mechanism inblade folded position;

FIG. 6 is an elevation similar to FIG. 4 showing the parts in bladefolded position;

FIG. 7 is a section on line 77 of FIG. 3 showing the scissors carried bythe blade spindle for rotating the blade connected part of the linkage;and

FIG. 8 is a view taken on line 8-8 of FIG. 7 showing a modifiedconstruction for changing blade pitch coupling characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. I and2. I0 indicates a hellcopter lift rotor supported from the helicoptorfuselage (not shown) by a hollow drive shaft I2 which is rotatable aboutaxis 14 and has at its upper end the hub assembly I6 from which fourblades 18. 20. 22. and 24 project for rotation therewith. Two of theblades I8 and 22 are mounted on the hub assembly on generally verticalfixed hinge pins 26 in bearings 28 so as to be folded thru an angle of90 in flight with respect to hub assembly [6 between an extended oroperable position and a folded or inoperative position in which they arestopped and stowed within or alongside the fuselage. Prior to folding ofblades 18 and 22. the other blades 20 and 24 will be indexed to a foreand aft position. In an alternative rotor system all four blades may befolded. In such case the blades would each be folded thru an angle of45.

Hinge pins 26 are fixed in the hub by locking members 27 best shown inFIGS. 1 and 4. The blades may be folded manually on the ground or theymay be folded in flight. Mechanism for such in-flight folding of allfour blades of the helicoptor is fully illustrated and described in U.S.Pat. No. 3.484.175. heretofore referred to. and reference is made tothis patent for a disclosure of this folding mechanism.

Each blade consists of a spindle 30. on which the blade cuff32 ismounted on stack bearings 34 for feathering movement of the blade aboutthe longitudinal axis 36 of the blade. In order to allow blades 18 and22 to fold relative to the hub assembly 16. the blade spindles 30 forthese blades are pivoted about fold pin 26. It will be noted that inthis rotor there is a slight amount of built-in coning of the bladesshown as the slight upward inclination ofthe axis 36. Other than thefeathering movement of the blade about spindle 32. the mounting of theblades on the hub is rigid. The cuff of each blade is provided with theusual born 38 (FIG. I outstanding from the blade cuff 32 which isconnected by linkage to the rotating part of the swashplatc assembly.The linkage of blade I8 and 22 is novel and will be fully describedhereinafter.

The swashplate assembly is mounted on the rotor drive shaft 12 forsliding movement axially of the shaft to change the pitch of all of theblades collectively and also for tilting movement for changing the pitchof the blades cyclically. To this end a collar is slidably mounted on asleeve 42 fixed on shaft 12. Collar 40 has a convex outer surface 44 onwhich a bearing 46 having a similarly concave inner surface can rock.The hub 48 of the swashplatc has inner flanges 50, 52 which form arecess to receive bearing 46. The upper flange 50 on hub 48 consists ofan annular washer-like plate which is detachably secured to hub 48 bycap screws (not shown) to permit assembly.

Outboard of its hub 48 the swashplate is provided with a boss 52a whichhouses a spherical bearing 54 through which the vertical stem 56 ofarotating scissors 58 extends. The upper end of stem 56 has an eye 57through which extends a pivot pin 60 mounted in the bifurcated end of abracket 62 secured to the rotary hub assembly by cap screws 64. Thus hub48 and the swashplate structure thus far described comprises therotatable portion of the swashplate. Farther outboard of hub 48 therotatable portion of the swashplate has four peripherally spaced lugs 66to which upwardly ex tending rods are pivoted on pins 69, one for eachblade. The upwardly extended rods to non-foldahle blades 20 and 24 areconnected directly to the horn 38, while the rods 68 which extend to thefoldablc blades 18 and 22 are connected to their horns 38 by means of mynovel linkage. Further discussion of control linkage will be limited tothat leading to the foldablc blades [8 and 22.

The non-rotating portion 70 of the swashplate is mounted on theperiphery of the rotatable portion on bearings 72 and carries three lugs74, 75, and 76, peripherally spaced 90 degrees apart from each other. towhich the three servomotors (not shown) are attached for tilting theswashplate in a usual manner. A lug 78 (FIGS. l and 2) is provided onthe periphery of the non-rotatable portion 70 of the swashplate to whichone end of a scissors 80 is attached by means of a spherical bearing.the other end of the scissors (not shown) being pivotally attached to afixed part of the airframe of the helicopter.

The present invention is principally concerned with the linkagemechanism between the rotatable portion ofthe swashplatc and the bladehorns 38 ofthe foldablc blades.

Herein. as shown most clearly in FIG. 2. the fold pin 26 for each bladeI8 and 22 has a depending. axial extension 82 which has an integralflange 84 that is secured to the lower end of the pin by cap screws 86.A first pivot arm 88 is pivoted on extension 82 on a horizontal pin 90in such manner as to permit arm 88 to move freely about its pivot. Tothis end arm 88 is formed with a chamber 92 to receive extension 82 andthe walls of the chamber are cut away at 93 to permit a wide angularmovement of arm 88. At its free end arm 88 is pivotally connected by apin 89 to the end of rod 68. the lower end of which is pivotallyconnected to lug 66 of the swashplate by pin 69. Herein pivot 90 for arm88 lies on the axis of fold pin 26.

The hub of first pivot arm 88 has an integral depending axial extension96 which carries a bearing sleeve 98 and forms the journal for the hubof a second pivot arm 100. An annular plate I02 secured to the endofcxtension 96 by cap screws I04 holds pivot arm [00 in posi tion toswing about the axis of the hub of first pivot arm 88. Pivot arm 100 hasan offset end 106 (FIG. 6) to which a rod [08 is connected by pivot pin110. The other end of rod I08 is connected to blade born 38 by a pivotpin 112. A scissors 116 is pivotally connected at 118 to the bladespindle 30 and has a depending stem [19 which passes through a sphericalbearing 120 in second pivot arm 10f causing the latter to pivot aboutextension 96 as the blade pivots about fold pin 26 dur' ing bladefolding.

From FIGS. 3 to 6 it will be noted that second pivot arm 100 lies belowfirst pivot arm 88 and in the ex tended position of the blade shown inFlG. 3 is angularly related to it. By reason of its offset. upturned end106. the free end of second pivot arm 100 lies alongside that of firstpivot arm 88. Thus in the extended position of the blade, pivot pins 89and H0 of the first and second pivot arms are aligned. Any verticalmovement of rod 68 by the swashplate results in a like vertical movementof rod 108, since arms 88 and 100 move together without relativemovement one to the other. Folding of the blade. however. results inswinging the second pivot arm [00 about its bearing 98 on first pivotarm 88. The latter does not move about its pivot 90 and consequentlythere is no change in blade pitch as a result of folding.

OPERATION ln diagrammatic views 3-6 the operation of the improvedlinkage mechanism this far described has been shown fora single blade.In the extended position of the blade (FlGS. 3 and 4) tilting of theswashplatc results in cyclic change in blade pitch during which rod 68is raised and lowered to swing first pivot arm 88 about its horizontalpivot 90. Since second pivot arm 100 is carried by the hub of pivot arm88 for movement relative to the latter only about a generally verticalaxis. pivot arm 100 will move with arm 88 as a unit to raise and lowerrod 108 connected to the blade horn. This joint movement of arms 88 and100 will result in increasing and decreasing the pitch of the blade.

Preliminary to folding the blades 18 and 22, the rotor is stopped andthe blades are indexed to bring blade 20 or 24 over the tail cone of thefuselage. All blades are then placed in neutral pitch. which is theposition ofthe parts shown in FIG. 4. With the above steps accomplished,folding of the blades 18 and 22 to the HO. 5 position will result inswinging arm 100, by scissors I [6, without change in blade pitch sincearm 100 moves about bearing 96 which is on the axis of fold pin 26.

In FIG. 8 a modified form of the invention is shown which providesnormal helicopter operation. without folding, with capability to varythe blade pitch to lead/- lag coupling by adjustment made on the ground.To accomplish this it is necessary only to provide a pin 122 in the hubof second pivot arm 100 which. upon angular adjustment of arm [00 on itsbearing 98 can be projected into one of several registering holes 124 inaxial extension 96 and bearing 98 of pivot arm 88 to lock pivot arm [00in its new position of angular adjustment relative to arm 88.Preferably. as shown in FIG. 8, the pin should be extended through theentire hub of arm 100. It will be understood that the FIG. 8modification is the same as that shown in FIG. 2 with the addition ofthe selectively positioned locking pin. With the HO. 8 modification thescissors [[6 can be omitted ifdcsired.

and additional clearance may be required between the ends of arms 88 and100.

It will be evident that by this invention it has been made possible by avery simple and reliable mechanism to select any desired blade couplingby on-the-ground adjustment from zero alpha up in a pitch increasing ordecreasing direction. or. if blade folding is desired. to fold bladeswithout interfering with blade pitch control. all without anydisconnection of linkage or other control mechanism.

While only two embodiments of the invention have been shown anddescribed herein. I do not wish to be limited to the particular detailedconstruction shown. as various modifications will be evident to oneskilled in this art which fall within the scope of the following claims.

I claim:

1. In a helicopter rotor. a drive shaft. a hub on said shaft including afold pin fixed in said hub having a depending axial extension. a blademounted on said pin for folding movement. said blade having a horn. aswashplate on said shaft having a portion rotatable with said shaft. afirst pivot arm pivotally mounted on the extension of said pin forpivotal movement about a horizontal axis. a first link pivotallyconnecting said first ivot arm to the rotatable portion of saidswashplate. a second pivot arm journalled on said first pivot arm forpivotal movement about an axis coincident with the axis of said pin. anda second link pivotally connecting said second pivot arm to said bladehorn.

2. In a helicopter rotor. a drive shaft. a huh on said shaft including afold pin fixed in said hub having a depending axial extension. a blademounted on said pin for folding movement. said blade having a horn. aswashplate on said shaft having a portion rotatable with said shaft. alirst pivot arm pivitally mounted on the extension of said pin forpivotal movement about a horizontal axis. said first pivot arm having adepending extension. at first link pivotally connecting said first pivotarm to the rotatable portion of said swashplate. a second pivot armjournalled on said depending extension of said first pivot arm. the axisof said journal normally coinciding with the axis of said pin. and asecond link pivotally connecting said second pivot arm to said bladeborn.

3. In a helicopter rotor. a drive shaft. a hub on said shaft including afold pin fixed in said tub having a depending axial extension. a blademounted on said pin for folding movement. said blade having a horn. aswashplate on said shaft having a portion rotatable with said shaft. afirst pivot arm pivotally mounted on the extension of said pin forpivotal movement about a horizontal axis. a first link pivotallyconnecting said first pivot arm to the rotatable portion of saidswashplate. a second pivot arm journalled on said first pivot arm forpivotal movement about an axis coincident with the axis of said pin. asecond link pivotally connecting said second pivot arm to said bladehorn, said second pivot arm being journalled below and angularly relatedto said first pivot arm in the flight position of the blade. and saidsecond pivot arm having its free end offset horizontally and upwardlyextended to bring the corresponding pivots for said first and secondlinks into alignment.

4. In a helicopter rotor. a drive shaft. a hub on said shaft including apin fixed in said hub. said pin having an axial depending extension. ablade spindle mounted on said pin for blade folding movement. a blademounted for pitch changing movements about the longitudinal axis of saidspindle. said blade having a horn. a swashplate on said shaft having aportion rotatable with said hub. a first pivot arm pivotally mounted onsaid fold pin extension for movement about a horizontal axis. a linkconnected at a point remote from the pivot of said first pivot arm forconnecting the latter with the rotatable portion of said svvashplatc. asecond pivot arm journalled on said first pivot arm for swingingmovement with said blade about the axis of said fold pin extension, anda second link connecting said second pivot arm at a point remote fromits journal to said blade horn.

5. The combination of claim 4 in which the horizontal pivotal axis ofsaid first pivot arm intersects the axis of said fold pin.

6. The combination of claim 5 in which the points on said first andsecond pivot arms at which said first and second links are connectedthereto are equidistant from the axis of said fold pin.

7. The combination ofclaim 5 in which a scissors carried at one of itsends by said blade spindle has its other end extended downward andoperativcly connected with said second pivot arm for swinging the latterabout said fold pin with said blade.

8. ln a helicopter. a generally vertical drive shaft. a hub on the upperend of said shaft including a fold pin fixed in said hub and having adepending extension. a blade spindle mounted on said pin for foldingmovement. a blade on said spindle having a blade horn for effectingfeathering movement of said blade about the longitudinal axis of saidspindle. a swashplate on said shaft having a fixed portion and arotatable portion. a first pivot arm mounted on a horizontal pivot whichintersects the axis of said fold pin. a link connecting the free end ofsaid first pivot arm with the movable portion of said swashplate. asecond pivot arm journalled on a depending extension of said first pivotarm which lies in the axis of said pin. a link pivotally connecting thefree end of said second pivot arm with said blade horn. said secondpivot arm being normally angularly positioned relative to said firstpivot arm and beneath the latter and having its free end horizontallyoffset and upwardly directed to bring the corresponding pivots for saidfirst and second links into alignment in the normal flight position ofthe blade. said second pivot arm having a spherical bearing located at apoint spaced from the axis of said hinge pin. and means for swingingsaid second pivot arm in unison with said blade spindle upon foldingmovement of said blade comprising a scissors pivotally supported at itsupper end on said blade spindle and having its other end depending andextended through said spherical bearing on said second pivot arm.

1. In a helicopter rotor, a drive shaft, a hub on said shaft including afold pin fixed in said hub having a depending axial extension, a blademounted on said pin for folding movement, said blade having a horn, aswashplate on said shaft having a portion rotatable with said shaft, afirst pivot arm pivotally mounted on the extension of said pin forpivotal movement about a horizontal axis, a first link pivotallyconnecting said first pivot arm to the rotatable portion of saidswashplate, a second pivot arm journalled on said first pivot arm forpivotal movement about an axis coincident with the axis of said pin, anda second link pivotally connecting said second pivot arm to said bladehorn.
 2. In a helicopter rotor, a drive shaft, a hub on said shaftincluding a fold pin fixed in said hub having a depending axialextension, a blade mounted on said pin for folding movement, said bladehaving a horn, a swashplate on said shaft having a portion rotatablewith said shAft, a first pivot arm pivitally mounted on the extension ofsaid pin for pivotal movement about a horizontal axis, said first pivotarm having a depending extension, a first link pivotally connecting saidfirst pivot arm to the rotatable portion of said swashplate, a secondpivot arm journalled on said depending extension of said first pivotarm, the axis of said journal normally coinciding with the axis of saidpin, and a second link pivotally connecting said second pivot arm tosaid blade horn.
 3. In a helicopter rotor, a drive shaft, a hub on saidshaft including a fold pin fixed in said tub having a depending axialextension, a blade mounted on said pin for folding movement, said bladehaving a horn, a swashplate on said shaft having a portion rotatablewith said shaft, a first pivot arm pivotally mounted on the extension ofsaid pin for pivotal movement about a horizontal axis, a first linkpivotally connecting said first pivot arm to the rotatable portion ofsaid swashplate, a second pivot arm journalled on said first pivot armfor pivotal movement about an axis coincident with the axis of said pin,a second link pivotally connecting said second pivot arm to said bladehorn, said second pivot arm being journalled below and angularly relatedto said first pivot arm in the flight position of the blade, and saidsecond pivot arm having its free end offset horizontally and upwardlyextended to bring the corresponding pivots for said first and secondlinks into alignment.
 4. In a helicopter rotor, a drive shaft, a hub onsaid shaft including a pin fixed in said hub, said pin having an axialdepending extension, a blade spindle mounted on said pin for bladefolding movement, a blade mounted for pitch changing movements about thelongitudinal axis of said spindle, said blade having a horn, aswashplate on said shaft having a portion rotatable with said hub, afirst pivot arm pivotally mounted on said fold pin extension formovement about a horizontal axis, a link connected at a point remotefrom the pivot of said first pivot arm for connecting the latter withthe rotatable portion of said swashplate, a second pivot arm journalledon said first pivot arm for swinging movement with said blade about theaxis of said fold pin extension, and a second link connecting saidsecond pivot arm at a point remote from its journal to said blade horn.5. The combination of claim 4 in which the horizontal pivotal axis ofsaid first pivot arm intersects the axis of said fold pin.
 6. Thecombination of claim 5 in which the points on said first and secondpivot arms at which said first and second links are connected theretoare equidistant from the axis of said fold pin.
 7. The combination ofclaim 5 in which a scissors carried at one of its ends by said bladespindle has its other end extended downward and operatively connectedwith said second pivot arm for swinging the latter about said fold pinwith said blade.
 8. In a helicopter, a generally vertical drive shaft, ahub on the upper end of said shaft including a fold pin fixed in saidhub and having a depending extension, a blade spindle mounted on saidpin for folding movement, a blade on said spindle having a blade hornfor effecting feathering movement of said blade about the longitudinalaxis of said spindle, a swashplate on said shaft having a fixed portionand a rotatable portion, a first pivot arm mounted on a horizontal pivotwhich intersects the axis of said fold pin, a link connecting the freeend of said first pivot arm with the movable portion of said swashplate,a second pivot arm journalled on a depending extension of said firstpivot arm which lies in the axis of said pin, a link pivotallyconnecting the free end of said second pivot arm with said blade horn,said second pivot arm being normally angularly positioned relative tosaid first pivot arm and beneath the latter and having its free endhorizontally offset and upwardly directed to bring the correspondingpivots for said first and second links into alignment in the normalflight position of the blade, said second pivot arm having a sphericalbearing located at a point spaced from the axis of said hinge pin, andmeans for swinging said second pivot arm in unison with said bladespindle upon folding movement of said blade comprising a scissorspivotally supported at its upper end on said blade spindle and havingits other end depending and extended through said spherical bearing onsaid second pivot arm.